Alarm systems are known in the art. For example, an alarm system can include a fire detection system or a life safety system. Wireless alarm systems throughout the world require monitoring for integrity and reporting tampering with individual devices in the system.
Specifically, for fire detection systems, section 62.2.1 of the Ninth Edition of UL (Underwriters Laboratories) 864 requires that removal of an initiating device transmitter from its installed location shall cause the immediate transmission of a tamper signal. Accordingly, wireless sensor devices employed in known fire detection systems have been equipped with systems to detect the displacement of the wireless device from an intended mounting location.
To achieve compliance with industry requirements, known alarm systems typically mount wireless sensing devices to a permanently fixed object. For example, many known alarm systems use screws to mount a wireless sensing device to grid work supporting removable ceiling tiles rather than to a ceiling tile itself. The wireless sensing device is equipped with an electromechanical limit switch that detects the removal of the cover over the mounting hardware within the device. However, the use of electromechanical devices adds additional cost as well as engineering design time.
In known alarm systems, the placement of the wireless sensing device is restricted, for example, to the grid work. However, the ideal placement of a sensing device may instead be on a ceiling tile for esthetic reasons or for a variety of environmental reasons. For example, it may be preferable to keep the sensing device away from an air duct, in the center of a space, or away from metallic objects. In architecturally significant or historical structures, the use of damaging mounting devices, such as deep screws, may be restricted.
There is thus a continuing, ongoing need for low-cost systems and methods that eliminate mounting restrictions of wireless sensing devices in an alarm system. Preferably, such systems and methods use acceleration vector analysis and filter algorithms, radio frequency triangulation, acoustic ultrasonic ranging, and/or light ranging to detect the displacement of a device or the tampering therewith.